Prepend to command line arguments in linux/bash - linux

I want to pass along the command line arguments given to script to another command, but I also want to add some additional arguments on the front first. How can I do this with bash?
This will send all the arguments through to the command:
command $#
But I want something more like:
command [argument1, argument2, $#]
How can you do something like this in bash?


#ThatOtherGuy's answer is correct.
If you were looking to "unshift" a couple of arguments into the positional parameters, do this:
set -- arg1 arg2 "$#"
cmd "$#"


If you have grep foo and you want to add -f before foo, you can use grep -f foo. The same thing applies here:
cmd argument1 argument2 "$#"


If you want a more generic way to do this (recommended), use this:
#!/usr/bin/env bash
function xyz {
echo "${args[#]}" # arguments will printed out
}
function abc {
local args=()
args+=(argument1)
args+=(argument2)
args+=("$#")
xyz "${args[#]}"
}
to test, source the above code
source script.sh && abc

Related

Passing values to a specific command in a chained command using an alias [duplicate]

I used to use CShell (csh), which lets you make an alias that takes a parameter. The notation was something like
alias junk="mv \\!* ~/.Trash"
In Bash, this does not seem to work. Given that Bash has a multitude of useful features, I would assume that this one has been implemented but I am wondering how.

Bash alias does not directly accept parameters. You will have to create a function.
alias does not accept parameters but a function can be called just like an alias. For example:
myfunction() {
#do things with parameters like $1 such as
mv "$1" "$1.bak"
cp "$2" "$1"
}
myfunction old.conf new.conf #calls `myfunction`
By the way, Bash functions defined in your .bashrc and other files are available as commands within your shell. So for instance you can call the earlier function like this
$ myfunction original.conf my.conf

Refining the answer above, you can get 1-line syntax like you can for aliases, which is more convenient for ad-hoc definitions in a shell or .bashrc files:
bash$ myfunction() { mv "$1" "$1.bak" && cp -i "$2" "$1"; }
bash$ myfunction original.conf my.conf
Don't forget the semi-colon before the closing right-bracket. Similarly, for the actual question:
csh% alias junk="mv \\!* ~/.Trash"
bash$ junk() { mv "$#" ~/.Trash/; }
Or:
bash$ junk() { for item in "$#" ; do echo "Trashing: $item" ; mv "$item" ~/.Trash/; done; }

The question is simply asked wrong. You don't make an alias that takes parameters because alias just adds a second name for something that already exists. The functionality the OP wants is the function command to create a new function. You do not need to alias the function as the function already has a name.
I think you want something like this :
function trash() { mv "$#" ~/.Trash; }
That's it! You can use parameters $1, $2, $3, etc, or just stuff them all with $#

TL;DR: Do this instead
Its far easier and more readable to use a function than an alias to put arguments in the middle of a command.
$ wrap_args() { echo "before $# after"; }
$ wrap_args 1 2 3
before 1 2 3 after
If you read on, you'll learn things that you don't need to know about shell argument processing. Knowledge is dangerous. Just get the outcome you want, before the dark side forever controls your destiny.
Clarification
bash aliases do accept arguments, but only at the end:
$ alias speak=echo
$ speak hello world
hello world
Putting arguments into the middle of command via alias is indeed possible but it gets ugly.
Don't try this at home, kiddies!
If you like circumventing limitations and doing what others say is impossible, here's the recipe. Just don't blame me if your hair gets frazzled and your face ends up covered in soot mad-scientist-style.
The workaround is to pass the arguments that alias accepts only at the end to a wrapper that will insert them in the middle and then execute your command.
Solution 1
If you're really against using a function per se, you can use:
$ alias wrap_args='f(){ echo before "$#" after; unset -f f; }; f'
$ wrap_args x y z
before x y z after
You can replace $# with $1 if you only want the first argument.
Explanation 1
This creates a temporary function f, which is passed the arguments (note that f is called at the very end). The unset -f removes the function definition as the alias is executed so it doesn't hang around afterwards.
Solution 2
You can also use a subshell:
$ alias wrap_args='sh -c '\''echo before "$#" after'\'' _'
Explanation 2
The alias builds a command like:
sh -c 'echo before "$#" after' _
Comments:
The placeholder _ is required, but it could be anything. It gets set to sh's $0, and is required so that the first of the user-given arguments don't get consumed. Demonstration:
sh -c 'echo Consumed: "$0" Printing: "$#"' alcohol drunken babble
Consumed: alcohol Printing: drunken babble
The single-quotes inside single-quotes are required. Here's an example of it not working with double quotes:
$ sh -c "echo Consumed: $0 Printing: $#" alcohol drunken babble
Consumed: -bash Printing:
Here the values of the interactive shell's $0 and $# are replaced into the double quoted before it is passed to sh. Here's proof:
echo "Consumed: $0 Printing: $#"
Consumed: -bash Printing:
The single quotes ensure that these variables are not interpreted by interactive shell, and are passed literally to sh -c.
You could use double-quotes and \$#, but best practice is to quote your arguments (as they may contain spaces), and \"\$#\" looks even uglier, but may help you win an obfuscation contest where frazzled hair is a prerequisite for entry.

All you have to do is make a function inside an alias:
$ alias mkcd='_mkcd(){ mkdir "$1"; cd "$1";}; _mkcd'
^ * ^ ^ ^ ^ ^
You must put double quotes around "$1" because single quotes will not work. This is because clashing the quotes at the places marked with arrows confuses the system. Also, a space at the place marked with a star is needed for the function.

Once I did some fun project and I'm still using it. It's showing some animation while copy files via cp command coz cp don't show anything and it's kind of frustrating. So I've made this alias for cp:
alias cp="~/SCR/spinner cp"
And this is the spinner script
#!/bin/bash
#Set timer
T=$(date +%s)
#Add some color
. ~/SCR/color
#Animation sprites
sprite=( "(* ) ( *)" " (* )( *) " " ( *)(* ) " "( *) (* )" "(* ) ( *)" )
#Print empty line and hide cursor
printf "\n${COF}"
#Exit function
function bye { printf "${CON}"; [ -e /proc/$pid ] && kill -9 $pid; exit; }; trap bye INT
#Run our command and get its pid
"$#" & pid=$!
#Waiting animation
i=0; while [ -e /proc/$pid ]; do sleep 0.1
printf "\r${GRN}Please wait... ${YLW}${sprite[$i]}${DEF}"
((i++)); [[ $i = ${#sprite[#]} ]] && i=0
done
#Print time and exit
T=$(($(date +%s)-$T))
printf "\n\nTime taken: $(date -u -d #${T} +'%T')\n"
bye
It looks like this
Cycled animation)
Here is the link to a color script mentioned above.
And new animation cycle)
So the answer to the OP's question is to use intermediate script that could shuffle args as you wish.

An alternative solution is to use marker, a tool I've created recently that allows you to "bookmark" command templates and easily place cursor at command place-holders:
I found that most of time, I'm using shell functions so I don't have to write frequently used commands again and again in the command-line. The issue of using functions for this use case, is adding new terms to my command vocabulary and having to remember what functions parameters refer to in the real-command. Marker goal is to eliminate that mental burden.

Syntax:
alias shortName="your custom command here"
Example:
alias tlogs='_t_logs() { tail -f ../path/$1/to/project/logs.txt ;}; _t_logs'

Bash alias absolutely does accept parameters. I just added an alias to create a new react app which accepts the app name as a parameter. Here's my process:
Open the bash_profile for editing in nano
nano /.bash_profile
Add your aliases, one per line:
alias gita='git add .'
alias gitc='git commit -m "$#"'
alias gitpom='git push origin master'
alias creact='npx create-react-app "$#"'
note: the "$#" accepts parameters passed in like "creact my-new-app"
Save and exit nano editor
ctrl+o to to write (hit enter); ctrl+x to exit
Tell terminal to use the new aliases in .bash_profile
source /.bash_profile
That's it! You can now use your new aliases

Here's are three examples of functions I have in my ~/.bashrc, that are essentially aliases that accept a parameter:
#Utility required by all below functions.
#https://stackoverflow.com/questions/369758/how-to-trim-whitespace-from-bash-variable#comment21953456_3232433
alias trim="sed -e 's/^[[:space:]]*//g' -e 's/[[:space:]]*\$//g'"
.
:<<COMMENT
Alias function for recursive deletion, with are-you-sure prompt.
Example:
srf /home/myusername/django_files/rest_tutorial/rest_venv/
Parameter is required, and must be at least one non-whitespace character.
Short description: Stored in SRF_DESC
With the following setting, this is *not* added to the history:
export HISTIGNORE="*rm -r*:srf *"
- https://superuser.com/questions/232885/can-you-share-wisdom-on-using-histignore-in-bash
See:
- y/n prompt: https://stackoverflow.com/a/3232082/2736496
- Alias w/param: https://stackoverflow.com/a/7131683/2736496
COMMENT
#SRF_DESC: For "aliaf" command (with an 'f'). Must end with a newline.
SRF_DESC="srf [path]: Recursive deletion, with y/n prompt\n"
srf() {
#Exit if no parameter is provided (if it's the empty string)
param=$(echo "$1" | trim)
echo "$param"
if [ -z "$param" ] #http://tldp.org/LDP/abs/html/comparison-ops.html
then
echo "Required parameter missing. Cancelled"; return
fi
#Actual line-breaks required in order to expand the variable.
#- https://stackoverflow.com/a/4296147/2736496
read -r -p "About to
sudo rm -rf \"$param\"
Are you sure? [y/N] " response
response=${response,,} # tolower
if [[ $response =~ ^(yes|y)$ ]]
then
sudo rm -rf "$param"
else
echo "Cancelled."
fi
}
.
:<<COMMENT
Delete item from history based on its line number. No prompt.
Short description: Stored in HX_DESC
Examples
hx 112
hx 3
See:
- https://unix.stackexchange.com/questions/57924/how-to-delete-commands-in-history-matching-a-given-string
COMMENT
#HX_DESC: For "aliaf" command (with an 'f'). Must end with a newline.
HX_DESC="hx [linenum]: Delete history item at line number\n"
hx() {
history -d "$1"
}
.
:<<COMMENT
Deletes all lines from the history that match a search string, with a
prompt. The history file is then reloaded into memory.
Short description: Stored in HXF_DESC
Examples
hxf "rm -rf"
hxf ^source
Parameter is required, and must be at least one non-whitespace character.
With the following setting, this is *not* added to the history:
export HISTIGNORE="*hxf *"
- https://superuser.com/questions/232885/can-you-share-wisdom-on-using-histignore-in-bash
See:
- https://unix.stackexchange.com/questions/57924/how-to-delete-commands-in-history-matching-a-given-string
COMMENT
#HXF_DESC: For "aliaf" command (with an 'f'). Must end with a newline.
HXF_DESC="hxf [searchterm]: Delete all history items matching search term, with y/n prompt\n"
hxf() {
#Exit if no parameter is provided (if it's the empty string)
param=$(echo "$1" | trim)
echo "$param"
if [ -z "$param" ] #http://tldp.org/LDP/abs/html/comparison-ops.html
then
echo "Required parameter missing. Cancelled"; return
fi
read -r -p "About to delete all items from history that match \"$param\". Are you sure? [y/N] " response
response=${response,,} # tolower
if [[ $response =~ ^(yes|y)$ ]]
then
#Delete all matched items from the file, and duplicate it to a temp
#location.
grep -v "$param" "$HISTFILE" > /tmp/history
#Clear all items in the current sessions history (in memory). This
#empties out $HISTFILE.
history -c
#Overwrite the actual history file with the temp one.
mv /tmp/history "$HISTFILE"
#Now reload it.
history -r "$HISTFILE" #Alternative: exec bash
else
echo "Cancelled."
fi
}
References:
Trimming whitespace from strings: How to trim whitespace from a Bash variable?
Actual line breaks: https://stackoverflow.com/a/4296147/2736496
Alias w/param: https://stackoverflow.com/a/7131683/2736496 (another answer in this question)
HISTIGNORE: https://superuser.com/questions/232885/can-you-share-wisdom-on-using-histignore-in-bash
Y/N prompt: https://stackoverflow.com/a/3232082/2736496
Delete all matching items from history: https://unix.stackexchange.com/questions/57924/how-to-delete-commands-in-history-matching-a-given-string
Is string null/empty: http://tldp.org/LDP/abs/html/comparison-ops.html

Respectfully to all those saying you can't insert a parameter in the middle of an alias I just tested it and found that it did work.
alias mycommand = "python3 "$1" script.py --folderoutput RESULTS/"
when I then ran mycommand foobar it worked exactly as if I had typed the command out longhand.

NB: In case the idea isn't obvious, it is a bad idea to use aliases for anything but aliases, the first one being the 'function in an alias' and the second one being the 'hard to read redirect/source'. Also, there are flaws (which i thought would be obvious, but just in case you are confused: I do not mean them to actually be used... anywhere!)
I've answered this before, and it has always been like this in the past:
alias foo='__foo() { unset -f $0; echo "arg1 for foo=$1"; }; __foo()'
which is fine and good, unless you are avoiding the use of functions all together. in which case you can take advantage of bash's vast ability to redirect text:
alias bar='cat <<< '\''echo arg1 for bar=$1'\'' | source /dev/stdin'
They are both about the same length give or take a few characters.
The real kicker is the time difference, the top being the 'function method' and the bottom being the 'redirect-source' method. To prove this theory, the timing speaks for itself:
arg1 for foo=FOOVALUE
real 0m0.011s user 0m0.004s sys 0m0.008s # <--time spent in foo
real 0m0.000s user 0m0.000s sys 0m0.000s # <--time spent in bar
arg1 for bar=BARVALUE
ubuntu#localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.010s user 0m0.004s sys 0m0.004s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
ubuntu#localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.011s user 0m0.000s sys 0m0.012s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
ubuntu#localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.012s user 0m0.004s sys 0m0.004s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
ubuntu#localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.010s user 0m0.008s sys 0m0.004s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
This is the bottom part of about 200 results, done at random intervals. It seems that function creation/destruction takes more time than redirection. Hopefully this will help future visitors to this question (didn't want to keep it to myself).

If you're looking for a generic way to apply all params to a function, not just one or two or some other hardcoded amount, you can do that this way:
#!/usr/bin/env bash
# you would want to `source` this file, maybe in your .bash_profile?
function runjar_fn(){
java -jar myjar.jar "$#";
}
alias runjar=runjar_fn;
So in the example above, i pass all parameters from when i run runjar to the alias.
For example, if i did runjar hi there it would end up actually running java -jar myjar.jar hi there. If i did runjar one two three it would run java -jar myjar.jar one two three.
I like this $# - based solution because it works with any number of params.

There are legitimate technical reasons to want a generalized solution to the problem of bash alias not having a mechanism to take a reposition arbitrary arguments. One reason is if the command you wish to execute would be adversely affected by the changes to the environment that result from executing a function. In all other cases, functions should be used.
What recently compelled me to attempt a solution to this is that I wanted to create some abbreviated commands for printing the definitions of variables and functions. So I wrote some functions for that purpose. However, there are certain variables which are (or may be) changed by a function call itself. Among them are:
FUNCNAME
BASH_SOURCE
BASH_LINENO
BASH_ARGC
BASH_ARGV
The basic command I had been using (in a function) to print variable defns. in the form output by the set command was:
sv () { set | grep --color=never -- "^$1=.*"; }
E.g.:
> V=voodoo
sv V
V=voodoo
Problem: This won't print the definitions of the variables mentioned above as they are in the current context, e.g., if in an interactive shell prompt (or not in any function calls), FUNCNAME isn't defined. But my function tells me the wrong information:
> sv FUNCNAME
FUNCNAME=([0]="sv")
One solution I came up with has been mentioned by others in other posts on this topic. For this specific command to print variable defns., and which requires only one argument, I did this:
alias asv='(grep -- "^$(cat -)=.*" <(set)) <<<'
Which gives the correct output (none), and result status (false):
> asv FUNCNAME
> echo $?
1
However, I still felt compelled to find a solution that works for arbitrary numbers of arguments.
A General Solution To Passing Arbitrary Arguments To A Bash Aliased Command:
# (I put this code in a file "alias-arg.sh"):
# cmd [arg1 ...] – an experimental command that optionally takes args,
# which are printed as "cmd(arg1 ...)"
#
# Also sets global variable "CMD_DONE" to "true".
#
cmd () { echo "cmd($#)"; declare -g CMD_DONE=true; }
# Now set up an alias "ac2" that passes to cmd two arguments placed
# after the alias, but passes them to cmd with their order reversed:
#
# ac2 cmd_arg2 cmd_arg1 – calls "cmd" as: "cmd cmd_arg1 cmd_arg2"
#
alias ac2='
# Set up cmd to be execed after f() finishes:
#
trap '\''cmd "${CMD_ARGV[1]}" "${CMD_ARGV[0]}"'\'' SIGUSR1;
# ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
# (^This is the actually execed command^)
#
# f [arg0 arg1 ...] – acquires args and sets up trap to run cmd:
f () {
declare -ag CMD_ARGV=("$#"); # array to give args to cmd
kill -SIGUSR1 $$; # this causes cmd to be run
trap SIGUSR1; # unset the trap for SIGUSR1
unset CMD_ARGV; # clean up env...
unset f; # incl. this function!
};
f' # Finally, exec f, which will receive the args following "ac2".
E.g.:
> . alias-arg.sh
> ac2 one two
cmd(two one)
>
> # Check to see that command run via trap affects this environment:
> asv CMD_DONE
CMD_DONE=true
A nice thing about this solution is that all the special tricks used to handle positional parameters (arguments) to commands will work when composing the trapped command. The only difference is that array syntax must be used.
E.g.,
If you want "$#", use "${CMD_ARGV[#]}".
If you want "$#", use "${#CMD_ARGV[#]}".
Etc.

I will just post my (hopefully, okay) solution
(for future readers, & most vitally; editors).
So - please edit & improve/remove anything in this post.
In the terminal:
$ alias <name_of_your_alias>_$argname="<command> $argname"
and to use it (notice the space after '_':
$<name_of_your_alias>_ $argname
for example, a alias to cat a file called hello.txt:
(alias name is CAT_FILE_)
and the $f (is the $argname, which is a file in this example)
$ alias CAT_FILE_$f="cat $f"
$ echo " " >> hello.txt
$ echo "hello there!" >> hello.txt
$ echo " " >> hello.txt
$ cat hello.txt
hello there!
Test (notice the space after '_'):
CAT_FILE_ hello.txt

As has already been pointed out by others, using a function should be considered best practice.
However, here is another approach, leveraging xargs:
alias junk="xargs -I "{}" -- mv "{}" "~/.Trash" <<< "
Note that this has side effects regarding redirection of streams.

Solution with subcommands:
d () {
if [ $# -eq 0 ] ; then
docker
return 0
fi
CMD=$1
shift
case $CMD in
p)
docker ps --all $#
;;
r)
docker run --interactive --tty $#
;;
rma)
docker container prune
docker image prune --filter "dangling=true"
;;
*)
docker $CMD $#
;;
esac
return $?
}
Using:
$ d r my_image ...
Called:
docker run --interactive --tty my_image ...

Here's the example:
alias gcommit='function _f() { git add -A; git commit -m "$1"; } ; _f'
Very important:
There is a space after { and before }.
There is a ; after each command in sequence. If you forget this after the last command, you will see > prompt instead!
The argument is enclosed in quotes as "$1"

To give specific answer to the Question posed about creating the alias to move the files to Trash folder instead of deleting them:
alias rm="mv "$1" -t ~/.Trash/"
Offcourse you have to create dir ~/.Trash first.
Then just give following command:
$rm <filename>
$rm <dirname>

Here is another approach using read. I am using this for brute search of a file by its name fragment, ignoring the "permission denied" messages.
alias loc0='( IFS= read -r x; find . -iname "*" -print 2>/dev/null | grep $x;) <<<'
A simple example:
$ ( IFS= read -r x; echo "1 $x 2 ";) <<< "a b"
1 a b 2
Note, that this converts the argument as a string into variable(s). One could use several parameters within quotes for this, space separated:
$ ( read -r x0 x1; echo "1 ${x0} 2 ${x1} 3 ";) <<< "a b"
1 a 2 b 3

Functions are indeed almost always the answer as already amply contributed and confirmed by this quote from the man page: "For almost every purpose, aliases are superseded by shell functions."
For completeness and because this can be useful (marginally more lightweight syntax) it could be noted that when the parameter(s) follow the alias, they can still be used (although this wouldn't address the OP's requirement). This is probably easiest to demonstrate with an example:
alias ssh_disc='ssh -O stop'
allows me to type smth like ssh_disc myhost, which gets expanded as expected as: ssh -O stop myhost
This can be useful for commands which take complex arguments (my memory isn't what it use t be anymore...)

For taking parameters, you should use functions!
However $# get interpreted when creating the alias instead of during the execution of the alias and escaping the $ doesn’t work either. How do I solve this problem?
You need to use shell function instead of an alias to get rid of this problem. You can define foo as follows:
function foo() { /path/to/command "$#" ;}
OR
foo() { /path/to/command "$#" ;}
Finally, call your foo() using the following syntax:
foo arg1 arg2 argN
Make sure you add your foo() to ~/.bash_profile or ~/.zshrc file.
In your case, this will work
function trash() { mv $# ~/.Trash; }

Both functions and aliases can use parameters as others have shown here. Additionally, I would like to point out a couple of other aspects:
1. function runs in its own scope, alias shares scope
It may be useful to know this difference in cases you need to hide or expose something. It also suggests that a function is the better choice for encapsulation.
function tfunc(){
GlobalFromFunc="Global From Func" # Function set global variable by default
local FromFunc="onetwothree from func" # Set a local variable
}
alias talias='local LocalFromAlias="Local from Alias"; GlobalFromAlias="Global From Alias" # Cant hide a variable with local here '
# Test variables set by tfunc
tfunc # call tfunc
echo $GlobalFromFunc # This is visible
echo $LocalFromFunc # This is not visible
# Test variables set by talias
# call talias
talias
echo $GlobalFromAlias # This is invisible
echo $LocalFromAlias # This variable is unset and unusable
Output:
bash-3.2$ # Test variables set by tfunc
bash-3.2$ tfunc # call tfunc
bash-3.2$ echo $GlobalFromFunc # This is visible
Global From Func
bash-3.2$ echo $LocalFromFunc # This is not visible
bash-3.2$ # Test variables set by talias
bash-3.2$ # call talias
bash-3.2$ talias
bash: local: can only be used in a function
bash-3.2$ echo $GlobalFromAlias # This is invisible
Global From Alias
bash-3.2$ echo $LocalFromAlias # This variable is unset and unusable
2. wrapper script is a better choice
It has happened to me several times that an alias or function can not be found when logging in via ssh or involving switching usernames or multi-user environment. There are tips and tricks with sourcing dot files, or this interesting one with alias: alias sd='sudo ' lets this subsequent alias alias install='sd apt-get install' work as expect (notice the extra space in sd='sudo '). However, a wrapper script works better than a function or alias in cases like this. The main advantage with a wrapper script is that it is visible/executable for under intended path (i.e. /usr/loca/bin/) where as a function/alias needs to be sourced before it is usable. For example, you put a function in a ~/.bash_profile or ~/.bashrc for bash, but later switch to another shell (i.e. zsh) then the function is not visible anymore.
So, when you are in doubt, a wrapper script is always the most reliable and portable solution.

alias junk="delay-arguments mv _ ~/.Trash"
delay-arguments script:
#!/bin/bash
# Example:
# > delay-arguments echo 1 _ 3 4 2
# 1 2 3 4
# > delay-arguments echo "| o n e" _ "| t h r e e" "| f o u r" "| t w o"
# | o n e | t w o | t h r e e | f o u r
RAW_ARGS=("$#")
ARGS=()
ARG_DELAY_MARKER="_"
SKIPPED_ARGS=0
SKIPPED_ARG_NUM=0
RAW_ARGS_COUNT="$#"
for ARG in "$#"; do
#echo $ARG
if [[ "$ARG" == "$ARG_DELAY_MARKER" ]]; then
SKIPPED_ARGS=$((SKIPPED_ARGS+1))
fi
done
for ((I=0; I<$RAW_ARGS_COUNT-$SKIPPED_ARGS; I++)); do
ARG="${RAW_ARGS[$I]}"
if [[ "$ARG" == "$ARG_DELAY_MARKER" ]]; then
MOVE_SOURCE_ARG_NUM=$(($RAW_ARGS_COUNT-$SKIPPED_ARGS+$SKIPPED_ARG_NUM))
MOVING_ARG="${RAW_ARGS[$MOVE_SOURCE_ARG_NUM]}"
if [[ "$MOVING_ARG" == "$ARG_DELAY_MARKER" ]]; then
echo "Error: Not enough arguments!"
exit 1;
fi
#echo "Moving arg: $MOVING_ARG"
ARGS+=("$MOVING_ARG")
SKIPPED_ARG_NUM=$(($SKIPPED_ARG_NUM+1))
else
ARGS+=("$ARG")
fi
done
#for ARG in "${ARGS[#]}"; do
#echo "ARGN: $ARG"
#done
#echo "RAW_ARGS_COUNT: $RAW_ARGS_COUNT"
#echo "SKIPPED_ARGS: $SKIPPED_ARGS"
#echo "${ARGS[#]}"
QUOTED_ARGS=$(printf ' %q' "${ARGS[#]}")
eval "${QUOTED_ARGS[#]}"

Bash discards command line arguments when passing to another bash shell

I have a big script (call it test) that, after stripping out the unrelated parts, comes down to just this using which I can explain my question:
#!/bin/bash
bash -c "$#"
This doesn't work as expected. E.g. ./test echo hi executes the only the echo and the argument disappears!
Testing with various inputs I can see only $1 is passed to bash -c ... and rest are discarded.
But if I use a variable like:
#!/bin/bash
cmd="$#"
bash -c "$cmd"
it works as expected for all inputs.
Questions:
1) I would like to understand why the double quotes don't "pass" the entire command line arguments to bash -c .... What am I missing here (that it works perfectly fine when using an intermediate variable)?
2) Why does bash discard the rest of the arguments (except $1) without any error messages?
For example:
bash -c "ls" -l -a hi hello blah
simply runs echo and hi hello blah doesn't result in any errors at all?
(If possible, please refer to the bash grammar where this behaviour is documented).

1) I would like to understand why the double quotes don't "pass" the entire command line arguments to bash -c .... What am I missing here (that it works perfectly fine when using an intermediate variable)?
From info bash #:
#
($#) Expands to the positional parameters, starting from one. When the expansion occurs within double quotes, each parameter expands
to a separate word. That is, "$#" is equivalent to "$1" "$2" ....
Thus, bash -c "$#" is equivalent to bash -c "$1" "$2" .... In the case of ./test echo hi invocation, the expression is expanded to
bash -c "echo" "hi"
2) Why does bash discard the rest of the arguments (except $1) without any error messages?
Bash actually doesn't discard anything. From man bash:
If the -c option is present, then commands are read from the first non-option argument command_string. If there are arguments after the command_string, they are assigned to the positional parameters, starting with $0.
Thus, for the command bash -c "echo" "hi", Bash passes "hi" as $0 for the "echo" script.
bash -c "ls" -l -a hi hello blah
simply runs echo and hi hello blah doesn't result in any errors at all?
According to the rules mentioned above, Bash executes "ls" script and passes the following positional parameters to this script:
$0: "-l"
$1: "-a"
$2: "hi"
$3: "hello"
$4: "blah"
Thus, the command actually executes ls, and the positional parameters are unused in the script. You can use them by referencing to the positional parameters, e.g.:
$ set -x
$ bash -c "ls \$0 \$1 \$3" -l -a hi hello blah
+ bash -c 'ls $0 $1 $3' -l -a hi hello blah
ls: cannot access hello: No such file or directory

You should be using $* instead of $# to pass command line as string. "$#" expands to multiple quoted arguments and "$*" combines multiple arguments into a single argument.
#!/bin/bash
bash -c "$*"
Problem is with your $# it executes:
bash -c echo hi
But with $* it executes:
bash -c 'echo hi'
When you use:
cmd="$#"
and use: bash -c "$cmd" it does the same thing for you.
Read: What is the difference between “$#” and “$*” in Bash?

Quoting with ssh command with a function call

I need to execute the shell command as follows:
ssh <device> "command"
command is invoked as:
$(typeset); <function_name> \"arguement_string\"; cd ...; ls ...
How exactly to quote here? Is this correct?
""$(typeset); <function_name> \"arguement_string\""; cd ...; ls ..."
I am confused with this quoting in shell scripts.

Don't try to do the quoting by hand -- ask the shell to do it for you!
command_array=( function_name "first argument" "second argument" )
printf -v command_str '%q ' "${command_array[#]}"
ssh_str="$(typeset); $command_str"
ssh machine "$ssh_str"
You can then build up command_array as you wish -- using logic to conditionally append values, with only the kind of quoting you'd usually refer to use to those values, and let printf %q add all additional quoting needed to make the content safe to pass through ssh.
If you're trying to incrementally build up a script, you can do that like so:
remote_script="$(typeset)"$'\n'
safe_append_command() {
local command_str
printf -v command_str '%q ' "$#"
remote_script+="$command_str"$'\n'
}
safe_append_command cp "$file" "$destination"
safe_append_command tar -cf /tmp/foo.tar "${destination%/*}"
# ...etc...
ssh machine "$remote_script"
Note that in this case, all expansions take place locally, when the script is being generated, and shell constructs such as redirection operators cannot be used (except by embedding them in a function you then pass to the remote system with typeset). Doing so means that no data passed to safe_append_command can be treated as code -- foreclosing large classes of potential security holes at the cost of flexibility.

I would use a here document:
ssh machine <<'EOF'
hello() {
echo "hello $1!"
}
hello "world"
EOF
Note that I wrapped the starting EOF in single quotes. Doing so prevents bash from interpreting variables or command substitutions in the local shell.

Positional parameters for shell not working as expected

I am trying to learn bash commands, and some very basic commands are not working as I expect...http://www.tutorialspoint.com/unix/unix-special-variables.htm
http://i.stack.imgur.com/F5VGK.png
Script:
#!/bin/bash
name="john"
other="shawn"
echo $name
echo $other
echo $1
echo $2
echo $#
echo $#
Output:
$ new
john
shawn
0
$

$1, $2, etc and $# have special meaning in bash scripts. They refer to the arguments passed to the bash script, so if you have a script in a file called foo.sh like:
#!/bin/bash
echo "Number of arguments: $#";
echo "First argument: $1";
echo "Second argument: $2";
If you chmod +x foo.sh and then run:
./foo.sh first second
You will see:
Number of arguments: 2
First argument: first
Second argument: second
$1 refers to the first command line argument passed to the script. The script is foo.sh, so anything after the script name will become a command line argument.
The default command line argument separator is the "space", so when you type ./foo.sh first second, bash stores first into $1 and second into $2.
If you typed:
./foo.sh first second third FOURTH fifth
bash would store third in the variable $3, FOURTH in the variable $4, and so on.

Is your script named 'new' ? In that case run it as follows one by one and you will get an idea how this works:
./new
./new a
./new a b

when you ran your script you did not pass any arguments. the number of arguments passed to the scripts are show by echoing "echo $#". and your output clearly shows that the "echo $#" command returned "0" count. pass the argument when you call your script like below
./new argument1 argument2

Pass command line arguments to another command in bash

I have a program which takes some command line arguments.
It's executed like this:
user#home $ node server.js SOME ARGUMENTS -p PORT -t THEME OTHER STUFF
Now I want to make a executable launcher for it:
#!/bin/bash
node server.js ARGUMENTS GIVEN FROM COMMAND LINE
How to do this?
I want to pass the same arguments to the command (without knowing how many and what they will be).
Is there a way?

Use the $# variable in double quotes:
#!/bin/bash
node server.js "$#"
This will provide all the arguments passed on the command line and protect spaces that could appear in them. If you don't use quotes, an argument like "foo bar" (that is, a single argument whose string value has a space in it) passed to your script will be passed to node as two arguments. From the documentation:
When the expansion occurs within double quotes, each parameter expands to a separate word. That is, "$#" is equivalent to "$1" "$2" ….
In light of the other answer, edited to add: I fail to see why you'd want to use $* at all. Execute the following script:
#!/bin/bash
echo "Quoted:"
for arg in "$*"; do
echo $arg
done
echo "Unquoted:"
for arg in $*; do
echo $arg
done
With, the following (assuming your file is saved as script and is executable):
$ script "a b" c
You'll get:
Quoted:
a b c
Unquoted:
a
b
c
Your user meant to pass two arguments: a b, and c. The "Quoted" case processes it as one argument: a b c. The "Unquoted" case processes it as 3 arguments: a, b and c. You'll have unhappy users.

Depending on what you want, probably using $#:
#!/bin/bash
node server.js "$#"
(Probably with quotes)
The thing to keep in mind is how arguments with e.g. spaces are handled. In this respect, $* and $# behave differently:
#!/usr/bin/env bash
echo '$#:'
for arg in "$#"; do
echo $arg
done
echo '$*:'
for arg in "$*"; do
echo $arg
done
Output:
$ ./test.sh a "b c"
$#:
a
b c
$*:
a b c

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